asp.netでenterkeyを無効にする方法

http://msdn.microsoft.com/ja-jp/library/cc766700.aspx

Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

form1.Attributes("onkeydown") = "if(event.keyCode==13){
if(window.event.srcElement.type!='submit' &&
window.event.srcElement.type!='textarea'){
return false;
}
}"

End Sub